This invention relates to leak detection in a pipe, and more particularly to a leak detection system that is based on displacement of structure under suction pressure resulting from a leak.
Considerable research and development (R&D) efforts are exerted around the world to develop technologies to detect water leaks in water distribution networks. Water leakage can reach 30% on average of the water transported across the water distribution networks [1, 2]. Current leak detection methods [3] include leak noise correlators, surface listening devices, ground penetrating radars, infrared thermography, and chemical tracing. These methods have many limitations when applied to actual water distribution networks. They can be expensive, time consuming, inaccurate, have noise interference problems, and depend on pipe material.
Acoustic and noise correlators [4, 5] are the widely used methods at the present time by water municipalities worldwide. These methods work well in metal pipes; however, the effectiveness of the method is diminished in plastic pipes due to high signal attenuation, low frequency content, and the pronounced effect of fittings on the wave propagation. Recently, leak detection using in-pipe moving sensors, like Sahara and Smartball systems, is considered to overcome many shortcomings of the conventional acoustic leak detection devices. The motivation for venturing into this technique stems from the ability to survey a long distance pipeline in a network, and surveying portions of the network which may be logistically difficult to access by other techniques. The closeness of the sensor to the leak location may enable capturing clean signals so leak detection and localization becomes more independent of pipe material, pipe depth, soil type, background noise, and other environmental effects.
Recently Atia et al [6] have proposed a leak detection method based on a pressure suction method which was first discovered using numerical techniques [7] and later experimentally verified by the same group. However, the method requires a large number (more than 20 for a 2 mm leak size) of pressure transducers or equivalent sensors in order to detect the leak. This requirement is mainly due to the fact that the pressure gradient caused by the leak is highly localized and its effect can only be sensed 1-2 leak diameters around the leak center.
It is therefore an object of the invention to provide a novel leak detection system that reduces considerably the number of sensors to a small number (3 to 5) and is capable of detecting a leak irrespective of its position around a pipe circumference. By reducing the number of sensors, the overall system cost is lower, reliability improves, and the amount of data to be processed is reduced as is the amount of power consumed.